Friend leukemia cells growing in suspension culture are induced to differentiate into the erythroid series when DMSO is added to their culture medium. During the past year we have found that DMSO corrects a metabolic defect in these leukemia cells permitting significant quantities of globin mRNA to accumulate and be translated into globin. BUdR interfers with DMSO-induction of differentiation by preventing the globin mRNA of FLC to increase. Our current studies are directed towards studying the reversibility of this process, developing methods which will further augment the differentiation of these leukemia cells, and to study the relationship between Friend leukemia virus and the state of differentiation of these cells.